This invention relates generally to a fuel injection nozzle for use in diesel engines which operate over a wide range of speed and load conditions, and pertains more particularly to a variable orifice type incorporating a pintle projecting into the orifice bore.
The following U.S. patents are representative of the pintle type injection valves known to the prior art: U.S. Pat. No. 2,860,010, issued Nov. 11, 1958 to Sennstrom et al; U.S. Pat. No. 3,045,920, issued July 24, 1962 to Hooker et al; and U.S. Pat. No. 3,444,886, issued May 20, 1969 to Bailey et al.
Such pintle type nozzles are known to the state-of-the-art, but a common problem with these nozzles is the difficulty in controlling the longitudinal motion, and therefore the orifice flow area, in response to the varying fluid pressure supplied to the nozzle assembly. This lack of control results in the pintle popping fully open, or at least an excessive amount initially or at low fluid discharge rates. The pintle also quite frequently undergoes an erratic motion, resulting in the orifice varying back and forth between large and small orifice openings during a single injection cycle. The large orifice opening causes a coarse fluid spray to be produced by the nozzle at low flow rates and pressures. This coarse spray results in poor combustion and waste of fuel.